1. Field of the Invention
The present invention relates to a method and apparatus for processing copyrighted data, and more specifically, to a method and apparatus for processing copyrighted data that is distributed through a network.
2. Description of the Background Art
In recent years, various digitized information has become widely available, and a large number of digital productions have been distributed with multimedia contents including images and sounds. Such digital productions are provided for users through recording media such as CD-ROMs or communication means such as the Internet. Downloading digital productions to personal computers through a communication network is especially a convenient distribution method, and therefore this method is expected to spread increasingly. Digital productions are easy to copy without deteriorating the characteristics thereof. For this reason, copyright protection for digital productions is highly required.
The following conventional arts have been known for protecting the copyright for digital productions. A first conventional art is a contents control method which is used in a music distribution system, which has been published in “Internet-based music distribution requires immediate improvements in copyright protection technologies”, Nikkei Electronics, Issue, no. 738, Mar., 8, 1999, PP. 87∝111. In the contents control method, a file containing encrypted music data (hereinafter referred to as file A) and a file containing control information, a decryption key for decrypting the file A, and other data (hereinafter referred to as file B) are distributed through a communication network. To play back the music data that is contained in the file A, it is determined, with reference to the control information contained in the file B, whether or not the file A is allowed to be played back or copied.
FIG. 17 is a block diagram showing the structure of a data processing apparatus which uses the first conventional art. The data processing apparatus shown in FIG. 17 is connected to a communication network (not shown) when the data processing apparatus is in use. A distributed data storage unit 101 stores the file A that is distributed through a communication network such as the Internet and CATV (Cable TV). A copyright management table 102 stores the file B that is distributed through the communication network in relation to the file A. A purchase process unit 103 communicates with a billing server (not shown) to purchase a process right that is required for playback and other processes, and records the purchased process right in the copyright management table 102. When an instruction is inputted by an input unit 104, a control unit 105 determines, with reference to the process right recorded in the copyright management table 102, whether the instruction is to be executed or not. A playback unit 106 receives a decryption key that is contained in the file B from the control unit 105, and plays back the music data that is contained in the file A.
As a second conventional art, a method of preventing unauthorized copying of digital data by encrypting the digital data has been known, which is disclosed in Japanese Patent Laid-Open Publication No. 9-320192 (1997-320192). FIG. 18 is a diagram showing the structure of a copyright protection apparatus according to the second conventional art. The copyright protection apparatus shown in FIG. 18 is characterized in that digital data that is read from a disk 111 is encrypted before being placed on a bus 114. In other words, a data format unit 112 provides the data that is read from the disk 111 with encryption start information, an encryption key, information about a unit of encryption, copy management information indicating whether data copying is allowed or not, and identification information of an encryption algorithm to be used. An encryption unit 113 encrypts the data by using the encryption key that is provided by a key delivery unit 110. The encrypted data flows on the bus 114. A decryption unit 115 decrypts the data by using a decryption key that is provided by the key delivery unit 110. The decrypted data is restored by a data format unit 116 to the state in which the digital data was read from the disk 111, and then the restored data is played back by a playback unit 117.
As such, according to the first conventional art, received copyrighted data can be processed within a purchased process right, while, according to the second conventional art, copyrighted data can be protected from unauthorized copying.
In these conventional arts, however, the process right that is required for processing copyrighted data is not presented to the user in an appropriate manner. Therefore, the user cannot recognize which process can be executed on each data item.